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Surface water pesticide monitoring results generally positive

OLYMPIA –  The amount of pesticides in two salmon-bearing watersheds is low and generally within acceptable levels, according to results from the first three years of the Washington’s ongoing surface water monitoring program.

The results were released today by the Washington state departments of Agriculture (WSDA) and Ecology (Ecology), which conducted the research in streams selected to be representative of urban and agricultural watersheds.

From 2003 to 2005, the study collected a total of 453 samples from the urban and agricultural sites. It analyzed for up to 160 chemicals; including 101 currently registered pesticides, pesticide breakdown products, and a number of historically used, but now banned pesticides, such as DDT.

The study found that during the three-year period, eight of the 101 currently registered pesticides were periodically found at levels that could potentially have impacts on aquatic health. Herbicides, which are chemicals used to control plants and weeds, were the most frequently detected pesticide in both urban and agricultural watershed.

“WSDA is working with applicators to implement mitigation measures to reduce pesticide exposure in salmon habitat,” said Bob Arrington, WSDA’s assistant director for pesticide management. “Future monitoring efforts will evaluate the success of mitigation strategies at reducing pesticide levels in surface waters and determine if further action is needed.”

In the study, scientists typically collected water samples weekly from March through October, which is the highest application period for pesticides.

The study found two general differences between the urban and agricultural drainages. Pentachlorophenol, a wood preservative having herbicidal properties was frequently detected in the urban watershed while insecticides, substances that control insects, were more frequently detected in the agricultural watershed.

The study authors, Jim Cowles of WSDA and Chris Burke of Ecology, conclude that restrictions on the use of two pesticides in urban areas, chlorophyrifos and diazinon, appear to have reduced the magnitude and frequency of detection of these compounds in the urban watershed.

In addition, the study found that DDT levels in the agricultural watershed appear to be declining. The authors believe this reduction is likely due to efforts by growers and the irrigation districts in the lower Yakima watershed to reduce sediment erosion.

For more information about the study results, visit the WSDA Web site at http://agr.wa.gov/PestFert/EnvResources/SWM/default.htm or the Ecology Web site at http://www.ecy.wa.gov/programs/eap/toxics/pesticides.html.
 

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